CN110832804A - Search spaces and configurations for short transmission time intervals - Google Patents
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Abstract
A method in a network node for supporting a predetermined set of aggregation levels for configuring a downlink control channel for one of a slotted Transmission Time Interval (TTI) and a sub-slotted TTI. The method comprises the following steps: determining an aggregation level to be monitored by a Wireless Device (WD) in a communication network; and determining a number of downlink control channel candidates to be monitored by WD within each of the slotted TTI and one of the sub-slotted TTI, the number of downlink control channel candidates being based on the aggregation level. A wireless apparatus and corresponding method are also provided for supporting a predetermined set of aggregation levels and for implementing at least one aggregation level and at least one downlink control channel candidate to configure a downlink control channel for one of a slotted TTI and a sub-slotted TTI.
Description
Technical Field
Wireless communication, and in particular, a method, network node and wireless device for configuring a downlink control channel for short transmission time intervals (sTTI).
Background
Packet data latency is one of the performance metrics that are regularly measured by the provider, operator, and end user (via the speed test application). The latency measurement is done in all phases of the radio access network system life when new software versions or system components are verified, when the system is deployed and when the system is in commercial operation.
Shorter latency than previous generations of 3GPP RATs has been a performance metric that has led to Long Term Evolution (LTE) designs. LTE is also now considered by end users as a system that provides faster internet access and lower data latency than previous generations of mobile radio technology.
Packet data latency is not only important to the perceptual responsiveness of the system; it is also a parameter that indirectly affects the system throughput. HTTP/TCP is the main application and transport layer protocol suite used on the internet today. Typical sizes of HTTP-based transactions on the Internet are in the range of 10 kilobytes to 1 megabyte, according to the HTTP archive (HTTP:// htpchicular. org/trends. php). Within this size range, the TCP slow start period is a significant portion of the total transmission period of the packet stream. During TCP slow start, performance is latency limited. Thus, improved latency can be shown quite easily for this type of TCP based data transaction to improve average throughput.
Radio resource efficiency can be positively affected by the reduction of latency. Lower packet data latency may increase the number of transmissions possible within a certain delay bound; thus, a higher block error rate (BLER) target may be used for data transmission that frees up radio resources, potentially increasing the capacity of the system.
One aspect to be addressed when it comes to packet latency reduction is to reduce the transmission time of data and control signaling by addressing the length of the Transmission Time Interval (TTI). In LTE release 8, a TTI corresponds to one Subframe (SF) of length 1 millisecond. One such 1ms tti is constructed by using 14 OFDM or SC-FDMA symbols in the case of a normal cyclic prefix, and one such 1ms tti is constructed by using 12 OFDM or SC-FDMA symbols in the case of an extended cyclic prefix.
Currently, work in the 3 rd generation partnership project (3GPP) (see RP-161299) is ongoing to standardize "short TTI" or "sTTI" operations in which scheduling and transmission can be done on a faster time scale. Thus, a legacy LTE subframe is subdivided into several sTTI. The supported lengths of sTTI of 2,4 and 7 OFDM symbols are currently discussed. Data transmission in the Downlink (DL) may occur in sTTI via a short physical downlink shared channel (sPDSCH), which may include a control region short downlink control channel (sPDCCH). In Uplink (UL), data is transmitted in sTTI via a short physical uplink shared channel (sPUSCH); control may be transmitted via a short physical uplink control channel (sPUCCH).
Different alternatives may schedule the sTTI in UL or DL to the wireless device. In one alternative, the respective wireless devices receive information about the sPDCCH candidates for the sTTI via RRC configuration telling the wireless devices where to look for the control channel for the sTTI, i.e., the sPDCCH. The DCI for the sTTI is actually directly included in the sPDCCH. In another alternative, the DCI for the sTTI is split into two parts, a slow DCI sent in the PDCCH and a fast DCI sent in the sPDCCH. The slow grant may contain frequency allocations for DL and UL short TTI frequency bands for short TTI operation, and it may also contain refinements regarding the sPDCCH candidate location.
The 3GPP Long Term Evolution (LTE) technology is a mobile broadband wireless communication technology in which transmissions from a base station (referred to as eNB) to a mobile station (also referred to as User Equipment (UE)) are transmitted using Orthogonal Frequency Division Multiplexing (OFDM). OFDM divides a signal into multiple parallel subcarriers in frequency. The basic unit of transmission in LTE is a Resource Block (RB), which in its most common configuration consists of 12 subcarriers and 7 OFDM symbols (one slot) with a normal cyclic prefix. In case of an extended cyclic prefix, an RB consists of 6 OFDM symbols in the time domain. The common term is also a Physical Resource Block (PRB) to indicate an RB in a physical resource. Two PRBs in the same subframe using the same 12 subcarriers represent a PRB pair. This is the smallest resource unit that can be scheduled in LTE.
A unit of one subcarrier and 1 OFDM symbol is called a Resource Element (RE) (see fig. 1). The PRB is thus composed of 84 REs. An LTE radio subframe consists of multiple resource blocks in frequency, where the number of PRBs determines the bandwidth of the system and two slots in time as shown in fig. 2.
In the time domain, the LTE downlink transmission is organized into 10ms radio frames, each radio frame being of length TsubframeTen equally sized subframes of 1 ms.
Messages transmitted over a radio link to a user may be broadly classified as control messages or data messages. The control messages are used to facilitate proper operation of the system and proper operation of each wireless device within the system. The control message may include a command to control a function, such as transmit power from the wireless device, signaling of RBs, etc., where data is to be received by or transmitted from the wireless device.
In Rel-8, the first to four OFDM symbols in a subframe are reserved to contain such control information, as shown in fig. 2, according to the configuration. Furthermore, in Rel-11, an enhanced control channel (EPDCCH) is introduced, where PRB-pairs (pair) are reserved to exclusively contain EPDCCH transmissions, although the first to four symbols, which may contain control information for wireless devices of a version earlier than Rel-11, are excluded from the PRB-pairs, see the diagram in fig. 3.
Thus, the EPDCCH is frequency multiplexed with PDSCH transmissions, as opposed to PDCCH which is time multiplexed with PDSCH transmissions. Depending on the Downlink Control Information (DCI) format, the Resource Allocation (RA) for PDSCH transmission exists in several RA types. Some RA types have a minimum scheduling granularity for a Resource Block Group (RBG), see 3GPP TS 36.211. An RBG is a set of adjacent (in frequency) resource blocks, and when a wireless device is scheduled, the wireless device is allocated resources in terms of RBGs rather than individual RBs.
When scheduling a wireless device from EPDCCH in the downlink, the wireless device assumes that PRB pairs carrying DL assignments are excluded from the resource allocation, i.e., rate matching is applied. For example, if the wireless device is scheduled PDSCH in a particular RBG that is 3 adjacent PRB pairs in size, and one of these PRB pairs contains a DL assignment, the wireless device assumes that PDSCH is transmitted only in the two remaining PRB pairs in that RBG. Note also that multiplexing of PDSCH and any EPDCCH transmissions within PRB-pairs is not supported in Rel-11.
The PDCCH and EPDCCH are transmitted on a radio resource shared between several User Equipments (UEs). Each PDCCH consists of a smaller part, called a Control Channel Element (CCE), to enable link adaptation (by controlling the number of CCEs the PDCCH is utilizing). It is specified that for PDCCH, a wireless device must monitor four (4) CCE aggregation levels, i.e., 1,2,4, and 8 for the wireless device specific search space, and 2 CCE aggregation levels, i.e., 4 and 8 for the common search space.
In section 9.1.1 of 3GPP TS36.213, the search space at the aggregation level L ∈ {1,2,4,8} is defined by a continuous set of CCEs given by
Wherein N isCCE,kIs the total number of CCEs in the control region of subframe k,define the start of the search space, i-0, 1(L)L-1, and M(L)Is the number of PDCCHs to be monitored in a given search space. Each CCE contains36 QPSK modulation symbols. M(L)The values of (d) are specified in 3GPP TS36.213 by tables 9.1.1-1, as follows:
TABLE 1
With this definition, search spaces of different aggregation levels may overlap each other regardless of system bandwidth. More specifically, the wireless device-specific search space and the common search space may overlap, and the search spaces for different aggregation levels may overlap. See one example shown below, where there are a total of 9 CCEs and very frequent overlap between PDCCH candidates:
example 1: n is a radical ofCCE,k9 for L ═ 1,2,4,8, respectively, are
(see table 2 below).
TABLE 2
After channel coding, scrambling, modulation, and interleaving of the control information, the modulated symbols are mapped to resource elements in the control region. In order to multiplex multiple PDCCHs onto a control region, Control Channel Elements (CCEs) have been defined, wherein each CCE is mapped to 36 resource elements. One PDCCH may consist of 1,2,4, or 8 CCEs depending on the information payload size and the required level of channel coding protection, and this number is denoted as CCE Aggregation Level (AL). By selecting the aggregation level, link adaptation for the PDCCH is obtained. Total N isCCEOne CCE may be used for all PDCCHs to be transmitted in a subframe, and NCCEThe number of which varies from subframe to subframe according to the number of control symbols n and the number of configured antenna ports.
Because of NCCEVarying from subframe to subframe, the wireless device needs to blindly determine the location and number of CCEs for its PDCCH, which may be computationally intensiveDecoding task of the set. Thus, some limitations on the number of possible blind decodes that the wireless device needs to experience have been introduced. For example, CCEs are numbered and a CCE aggregation level of size K may only start on CCE numbers that are evenly divisible by K, as shown in fig. 4.
The set of candidate control channels formed by CCEs in which a wireless device needs to blindly decode and search for a valid PDCCH is referred to as a search space. This is the set of CCEs on an AL that the wireless device should monitor for scheduling assignments or other control information, see the example in fig. 5, in each subframe and on each AL the wireless device will attempt to decode all PDCCHs that may be formed by CCEs in its search space. If the CRC checks, the content of the PDCCH is considered valid for the wireless device, and it further processes the received information. Two or more wireless devices will typically have overlapping search spaces and the network must select one of them to schedule the control channel. When this occurs, the non-scheduled wireless device is said to be blocked. The search space varies pseudo-randomly from subframe to minimize this blocking probability.
The search space is further divided into a common portion and a wireless device specific portion. In the common search space, the PDCCH containing information (paging, system information, etc.) is transmitted to all or one group of wireless devices. If carrier aggregation is used, the wireless device will only find the common search space that exists on the Primary Component Carrier (PCC). The common search space is limited to aggregation levels 4 and 8 in order to provide sufficient channel code protection for all wireless devices in the cell (link adaptation cannot be used since it is a broadcast channel). Front m with AL of 8 or 48And m4The individual PDCCHs (in which the CCE number is the smallest) belong to the common search spaces, respectively. To make efficient use of CCEs in the system, the remaining search space is wireless device specific at each aggregation level.
Fig. 5 is a diagram illustrating the search space (denoted as "a") that a particular wireless device needs to monitor. In this example there is a total of N CCE15 CCEs and the common search space is indicated as "B".
A CCE consists of 36 QPSK modulated symbols, which map to 36 REs unique to the CCE. To maximize diversity and interference randomization, interleaving of all CCEs is used before cell-specific cyclic shift and mapping to REs, see the processing steps in fig. 6. Note that in most cases, some CCEs are empty due to PDCCH location restrictions on wireless device search space and aggregation level. Null CCEs are included in the interleaving process and mapped to REs as any other PDCCH to maintain the search space structure. The null CCE is set to zero power and this power may instead be used by non-null CCEs to further enhance PDCCH transmission.
Furthermore, to be able to use 4-antenna TX diversity, groups of 4 adjacent QPSK symbols in a CCE are mapped to 4 adjacent REs, denoted as RE groups (REGs). Thus, CCE interleaving is a quadruple (quadruplex) based interleaving (4 groups), and the mapping process has a granularity of 1 REG, and one CCE corresponds to 9 REGs (═ 36 REs).
There will also typically be a set of REGs that have been sized NCCEIs still left as a residual resource after the CCE aggregation (although the residual REGs are always less than 36 REs) because the number of REGs available for PDCCH in the system bandwidth is typically not an even multiple of 9 REGs. These remaining REGs are not used by the system in LTE.
Similar to PDCCH, EPDCCH is transmitted on a radio resource shared by multiple wireless devices, and enhanced CCEs (ecces) are introduced as equivalents of CCEs for PDCCH. ecces also have a fixed number of REs, but the number of REs available for EPDCCH mapping is typically less than the fixed number, since many REs are occupied by other signals such as CRS and CSI-RS. Code chain rate matching is applied whenever REs belonging to ecces contain other colliding signals, such as CRS, CSI-RS, legacy control region, or GP and UpPTS in the case of TDD.
Consider the example shown in fig. 7, where (a) shows PDCCH mapping, which avoids CRS, so that CCEs always consist of available REs. In (b), it is shown how an eCCE nominally (nominally) includes 36 REs, but in case of a colliding signal, the number of available REs is small, and thus the REs are used for EPDCCH. Since the collision signal is subframe dependent, the value of the collision signal also becomes subframe dependent, and may even be different for different ecces if the collision affects ecces non-uniformly.
It should be noted that when the number of ecces per PRB pair is 2, the nominal number of REs per eCCE is not 36, but instead is 72 or 64 for normal and extended CP lengths, respectively.
In 3GPP Rel-11, EPDCCH supports only wireless device specific search space, while common search space remains monitored in PDCCH in the same subframe. In future versions, a common search space may also be introduced for EPDCCH transmission.
Wireless devices are provisioned to monitor eCCE aggregation levels 1,2,4,8, 16, and 32, where restrictions are shown.
In distributed transmission, EPDCCH is mapped to resource elements in up to D PRB-pairs, where D-2, 4 or 8 (the value of D-16 is also considered in 3 GPP). In this way, frequency diversity can be achieved for EPDCCH messages. See the schematic example of fig. 8.
Fig. 8 shows a downlink subframe showing that 4 parts belonging to EPDCCH are mapped to multiple enhanced control regions called PRB-pairs for distributed transmission and frequency diversity or subband precoding.
In localized (localized) transmission, EPDCCH is only mapped to one PRB-pair if the space allows (which is always possible for aggregation levels one and two and also for normal subframe and normal CP length also for level four). In case the aggregation level of the EPDCCH is too large, also the second PRB-pair is used, and so on, more PRB-pairs are used until all ecces belonging to the EPDCCH have been mapped.
Fig. 9 provides an illustration of centralized transmission. In particular, fig. 9 illustrates a downlink subframe showing that 4 ecces belonging to an EPDCCH are mapped to one of enhanced control regions to enable localized transmission.
As an example, in a normal subframe, and with a normal CP length and with nEPDCCHMore than or equal to 104, centralized transmission is using aggregationLevel (1, 2,4, 8), and they are respectively mapped to (1, 1, 1, 2) PRB pairs.
To facilitate mapping of ecces to physical resources, each PRB pair is divided into 16 enhanced resource element groups (eregs), and each eCCE is divided into 4 eregs for the normal cyclic prefix and 8 eregs for the extended cyclic prefix, respectively. Thus, EPDCCH is mapped to multiples of four or eight eregs depending on the aggregation level.
The eregs belonging to the ePDCCH reside in a single PRB pair (which is typical for localized transmission) or multiple PRB pairs (which is typical for distributed transmission). PRB pairs are accurately divided into eregs.
To rapidly schedule low latency data over a short TTI, a new short pdcch (spdcch) may be defined. Since short TTI operation is expected to co-exist with legacy TTI operation, the sPDCCH should be placed in-band within the PDSCH, still leaving resources for legacy data.
The legacy control channels PDCCH and EPDCCH are demodulated using CRS and DMRS, respectively. For operation in both environments, the sPDCCH should support both CRS and DMRS, and to be effectively maintained, the resources not used by the sPDCCH should be used by the sPDSCH (short PDSCH).
To facilitate the definition of sPDCCH mapped to resource elements, special entities are defined: short resource element group (sREG) and sCCE. This follows the method used so far in the LTE specification to define PDCCH and ePDCCH as described above. Note that the definition of the same mapping can also be done without using these terms or by using equivalent terms.
The main candidate length of sPDCCH in the time domain is 1 or 2 OFDM symbols for sTTI operation. REs of PRBs in a given OFDM symbol of an sTTI may construct one or more sregs. The number of REs in sREG may also be variable to provide allocation flexibility and support good frequency diversity.
The sREG configuration for sPDCCH is defined as the complete number of REs in a PRB within 1 OFDM symbol (i.e., 12 REs per sREG in 1 OFDM symbol). In fig. 10, these sREG configurations are depicted considering 1 OFDM symbol sPDCCH, 2 OFDM symbols sPDCCH, and 3OFDM symbols sPDCCH. Each index, namely {0, 1, 2} (denoted A, B and C, respectively), represents an sREG group.
The number of sregs required to establish scces for a given sPDCCH and their arrangement may vary along the frequency resources used for sTTI operation. One option is to define an sCCE, such as eCCE or CCE, ideally consisting of 36 REs. For this reason, and based on fig. 10, sCCE consists of three sregs, i.e., 1sCCE — 3 sregs.
For DMRS-based sPDCCH, another option considered to increase the number of available REs within 2 OFDM symbols sPDCCH is that sCCE is defined to consist of 48 REs instead of 36 REs, i.e., 1 sCCE-4 sregs. Compared to CRS based sPDCCH, 12 additional REs help to compensate for DMRS overhead.
To support good frequency diversity or more localized placement, localized and distributed placement schemes of sregs that build the same scces are defined:
-a centralized approach: sregs that construct the same scces may be localized in the frequency domain to allow for sPDCCH resource allocation that is confined in a limited band. This facilitates the use of beamforming for DMRS based sPDCCH.
-a distributed scheme: distributed sREG locations may be used to allow frequency diversity gain. In this case, multiple wireless devices may map sregs of their spdcchs to the same PRB on different REs. Distribution over a wide frequency range also makes it easier to fit the sPDCCH into one single OFDM symbol. User-specific beamforming with distributed sCCE locations is not recommended for wireless devices with DMRS based demodulation.
The schemes described below for constructing scces based on 1 OFDM symbol sPDCCH, 2 OFDM symbol sPDCCH, and 3OFDM symbol sPDCCH may be used for CRS and DMRS transmission.
Again, this takes into account the following considerations:
CRS and DMRS users may coexist on the same sTTI because the sPDCCH design is the same.
-if both CRS and DMRS users are given DCI in the same PRB, this needs to be used to indicate CRS users. Then, they know that some REs are not used for sCCE. Otherwise, DCI must be transmitted to CRS and DMRS users in different PRBs.
Each user configures at least one set of PRBs that can be used for sPDCCH. It has been recommended to support the configuration of several PRB sets for sPDCCH, so that one set of PRBs is configured after localized sPDCCH mapping, while another set of PRBs is configured with distributed mapping. The wireless device will monitor both sets and the network node may select the most favorable configuration/PRB set for a given sTTI and wireless device.
The set of PRBs assigned by the sPDCCH may be configured via RRC signaling to include PRBs from the available sTTI frequency band (not necessarily contiguous). However, it may include potential resource allocation refinements in slow DCI transmitted in PDCCH, e.g. a reduced set of PRBs or a specific set if several sPDCCH sets are defined.
The set of PRBs may be independently configured, for example, as a PRB bitmap. The set may also be configured based on a set of PRBs. One example of a PRB group that has been defined in LTE is called RBG and can be used as a basis in the proposed sPDCCH mapping. All PRBs within the same PRB group (e.g., RBG) are then used jointly.
The PRBs or groups of PRBs included in the configured set of PRBs may be ordered according to a sequence signaled to the wireless device prior to mapping the sPDCCH to the wireless device.
Due to the advantage of early decoding of 2 OFDM symbols sTTI and slot TTI, 1 OFDM symbol sPDCCH is defined for CRS based transmission. The 2 OFDM symbols sPDCCH may also be configured for 2 OFDM symbols sTTI and slot TTIs as an alternative to allowing a small sTTI frequency band, i.e. limiting the amount of frequency resources for sTTI operation.
For DMRS based transmissions with 2 OFDM symbols sTTI, assuming a DMRS pair design in the time domain as in conventional LTE, 2 OFDM symbols sPDCCH are defined, since the wireless device needs to wait for the end of the sTTI anyway for channel estimation. In this case, the DMRS is therefore not shared between sPDCCH and sPDSCH in a given PRB of the sTTI. This provides more freedom for applying beamforming to the sPDCCH. Furthermore, for some sTTI in a subframe, the TTI length is 3 symbols instead of 2 symbols. To allow flexibility in beamforming, a 3-symbol sPDCCH may be considered for a 3-symbol long sTTI.
For DMRSs with 1 slot sTTI, 2 symbol sPDCCH is suitable. Preferably, one DMRS pair for a 1-slot TTI enables channel estimation and early sPDCCH decoding for the sPDCCH. Also, the 3OFDM symbol sPDCCH is also applicable for 1-slot TTIs for those cases where only a small number of REs are available within the first 2 symbols in the slot due to reference signals and other kinds of overhead. Thus, given the presence of potential reference signals in sTTI such as DMRS, CRS, or CSI-RS, those REs occupied by these signals within a PRB are not used for a given sREG.
Assuming that the sPDCCH spans only the first OFDM symbol of 2 symbols sTTI and the sCCE consists of 36 REs (such as ECCE or CCE), 3 PRBs are needed to construct the sCCE (i.e., 3 sregs). These 3 PRBs may be distributed over the sPDCCH-PRB set or may be concentrated into three consecutive PRBs. In fig. 11, examples of distributed and centralized configurations are depicted for 4 scces and 1 OFDM symbol sPDCCH (unused PRBs shown in fig. 11 may be further assigned for constructing other scces and for the possibility of sPDSCH allocation). Fig. 11 relates to the case where the sPDCCH is configured in time with only 1 OFDM symbol (i.e. only OS1 is considered), for clarity sake sCCE0 is indicated as "0", sCCE1 is indicated as "1", sCCE2 is indicated as "2", and sCCE3 is indicated as "3".
The same considerations described above for 1 OFDM symbol sPDCCH can be extended to 2 OFDM symbols sPDCCH. The 2 OFDM symbols are suitable for CRS based sPDCCH transmission over poor channel conditions or for short TTI operation within a smaller frequency region. Also, as mentioned above, the 2 OFDM symbols sPDCCH are more suitable for DMRS based transmission.
If three sregs are needed to construct sCCE, there are two mapping options to consider for 2 OFDM symbols sPDCCH. In fig. 12, these options, including examples of distributed and centralized configurations, are depicted for 4 scces and 2 OFDM symbols sPDCCH (the unused PRBs shown in fig. 12 may be further assigned for constructing other scces and possibly for sPDSCH allocation). For clarity, sCCE0 is denoted as "0", sCCE1 is denoted as "1", sCCE2 is denoted as "2", and sCCE3 is denoted as "3".
In option a (fig. 12-left), sregs forming sCCE are selected in the following order: time-first-frequency-second. Thus, it is possible to utilize the 2 OFDM symbols available per PRB from the beginning. However, option a includes low frequency diversity of sregs in a distributed configuration. On the other hand, in option B (fig. 6-right), sregs forming sCCE are selected in the following order: frequency-first-time-second. With option B, higher frequency diversity of sREG can be achieved. For both options, the centralized configuration includes the same conditions.
In fig. 11 and 12, the physical resource blocks shown are consecutively numbered in frequency order and transmitted at the same time. The symbols (OS1 and OS2) are transmitted at separate times (consecutively). In fig. 12, "time-first-frequency-second" (option a) means that sregs are allocated for different times (symbols) and the same PRB (i.e., frequency) in the sPDCCH until no further time allocations (symbols) are available. The next allocated PRB (which may be contiguous or non-contiguous in a different set of frequencies) is then used. In option B of fig. 12, the references to time (symbols) and frequency (PRB) are reversed. It should be noted that even if PRBs are consecutively numbered in the figure, they are not necessarily physically consecutive PRBs from the available sTTI frequency band. It is simply the set of PRBs selected by the network node.
As described above, if 1sCCE is 4 sregs, then for 2 OFDM symbols sPDCCH, the sCCE consists of 2 full PRBs, as shown in fig. 13, showing an example of a distributed and centralized configuration of 4 scces (the unused PRBs shown in fig. 13 may be further assigned for constructing other scces and possibly for sPDSCH allocation). Fig. 12 and 13 relate to the case of 2 OFDM symbols sPDCCH (i.e. consider OS1 and OS 2). For clarity, sCCE0 is denoted as "0", sCCE1 is denoted as "1", sCCE2 is denoted as "2", and sCCE3 is denoted as "3".
For the case of 3OFDM symbols, sPDCCH based on DMRS-based transmission can be constructed with 1sCCE consisting of 3 sregs along 3 symbols with one full PRB for both 2os-sTTI (for the 3-symbol sTTI case) and slot-sTTI (with high reference signal overhead). Fig. 14 shows an example of a distributed and centralized configuration for 4 scces and 3OFDM symbols sPDCCH (the unused PRBs shown in fig. 14 may be further assigned for constructing other scces and possibly for sPDSCH allocation). Fig. 14 relates to the case of 3OFDM symbols sPDCCH (i.e. considering OS1, OS2 and OS 3). For clarity, sCCE0 is denoted as "0", sCCE1 is denoted as "1", sCCE2 is denoted as "2", and sCCE3 is denoted as "3".
The configuration of the DL control channel (sTTI) for the short TTI, referred to herein as sPDCCH (PDCCH for the short TTI), is configured by higher layer signaling or is predefined in the specification. Some of those configurations, such as the search space and the sPDCCH-PRB set(s) of the wireless device for sTTI operation, still need to be defined as included in the specification.
Disclosure of Invention
The present disclosure advantageously provides a method, network node and wireless device for supporting a predetermined set of aggregation levels for configuring downlink control channels for sTTI, to limit the number of blind decodes to be performed by the Wireless Device (WD) in some embodiments, and/or to provide flexibility in transmission of downlink control channels for sTTI in a network node in some embodiments.
Some embodiments disclosed herein include a method, a network node and a wireless device whereby in sTTI operation a limited number of aggregation levels and sPDCCH candidates for the wireless device may be configured within a 1ms subframe. Furthermore, an sPDCCH-PRB set configuration is proposed herein, comprising a definition for determining an sPDCCH-PRB set size to be configured for a wireless device or several wireless devices sharing the same PRB set.
According to an aspect of the present disclosure, a method in a network node for supporting a predetermined set of aggregation levels for configuring downlink control channels for short transmission time intervals (sTTI) is provided. The method comprises determining at least a subset of a predetermined set of aggregation levels to be monitored by a wireless device WD in the communication network; and determining a number of downlink control channel candidates to be monitored by WD within each sTTI, the number of downlink control channel candidates being based at least in part on at least a subset of the predetermined set of aggregation levels.
According to this aspect, in some embodiments, the method further comprises assigning the aggregation level and the downlink control channel candidates to the WD. In some embodiments, assigning the aggregation level and the downlink control channel candidates to the WD comprises assigning the aggregation level and the downlink control channel candidates to the WD by higher layers and optionally by RRC signaling. In some embodiments, determining the number of downlink control channel candidates to be monitored by WD within each of the one of a slotted TTI and a sub-slotted TTI comprises determining the number of downlink control channel candidates to be monitored by WD within each of the one of the slotted TTI and the sub-slotted TTI based on at least a maximum of six downlink control channel candidates to be monitored within each of the one of the slotted TTI and the sub-slotted TTI. Reference to "each of one of a slot TTI or a sub-slot TTI" may refer to a slot TTI and/or a sub-slot TTI, i.e., a short TTI.
In some embodiments, determining the number of downlink control channel candidates to be monitored by the wireless device within each of one of the slotted TTI and the sub-slotted TTI includes determining up to two downlink control channel candidates in a high aggregation level. In some embodiments, the sum of the number of downlink control channel candidates for each aggregation level according to the predetermined set of aggregation levels is at most six downlink control channel candidates. In some embodiments, one of the slot TTI and the sub-slot TTI is a short TTI. In some embodiments, the downlink control channel is a short physical downlink control channel (sPDCCH). In some embodiments, the aggregation level includes a number of short control channel elements (scces). In some embodiments, the number of scces supports a number of downlink control channel candidates defined for each aggregation level of the predetermined set of aggregation levels to be monitored by the WD. In some embodiments, the number of scces is determined based on the system bandwidth. In some embodiments, the number of scces is selected to avoid control overhead of available frequency resources along each of the one of the slot TTI and the sub-slot TTI. In some embodiments, the method further comprises determining a downlink control channel-Physical Resource Block (PRB) set size for each WD. In some embodiments, determining the PRB set size for each WD is based at least on a number of scces, a number of Orthogonal Frequency Division Multiplexing (OFDM) symbols per control channel, and a number of short resource element groups (sregs) per sCCE. In some embodiments, for a demodulation reference signal (DMRS) -based short physical downlink control channel (sPDCCH), two PRB sets are defined for the WD, a first PRB set being configured as localized and a second PRB set being configured as distributed.
According to another aspect of the present disclosure, a network node for supporting a predetermined set of aggregation levels for configuring a downlink control channel for one of a slotted Transmission Time Interval (TTI) and a sub-slotted TTI is provided. The network node comprises processing circuitry configured to: determining an aggregation level to be monitored by a Wireless Device (WD) in a communication network; and determining a number of downlink control channel candidates to be monitored by WD within each of one of the time slot TTI and the sub-time slot TTI, the number of downlink control channel candidates being based on the aggregation level.
According to this aspect, in some embodiments, the processing circuit is further configured to assign an aggregation level and downlink control channel candidates to the WD. In some embodiments, the processing circuit is further configured to assign the aggregation level and the downlink control channel candidates to the WD through higher layers and optionally through RRC signaling. In some embodiments, the processing circuit is further configured to determine a number of downlink control channel candidates to be monitored by WD within each of the one of the time-slot TTI and the sub-slot TTI based at least on a maximum of six downlink control channel candidates to be monitored within each of the one of the time-slot TTI and the sub-slot TTI. In some embodiments, the processing circuit is further configured to determine up to two downlink control channel candidates in a high aggregation level. In some embodiments, the sum of the number of downlink control channel candidates for each aggregation level according to the predetermined set of aggregation levels to be monitored by the WD is at most six downlink control channel candidates. In some embodiments, one of the slot TTI and the sub-slot TTI is a short TTI. In some embodiments, the downlink control channel is a short physical downlink control channel (sPDCCH). In some embodiments, the aggregation level includes a number of short control channel elements (scces). In some embodiments, the number of scces supports a number of downlink control channel candidates defined for each aggregation level of the predetermined set of aggregation levels to be monitored by the WD. In some embodiments, the number of scces is determined based on the system bandwidth. In some embodiments, the number of scces is selected to avoid control overhead of available frequency resources along each of the slot TTIs and the sub-slot TTIs. In some embodiments, the processing circuitry is further configured to determine a downlink control channel-Physical Resource Block (PRB) set size for each WD. In some embodiments, the processing circuitry is further configured to determine a PRB set size for each WD based at least on the number of scces, the number of Orthogonal Frequency Division Multiplexing (OFDM) symbols per control channel, and the number of short resource element groups (sregs) per sCCE. In some embodiments, the processing circuitry is further configured to define two sets of PRBs for a demodulation reference signal (DMRS) -based short physical downlink control channel (sPDCCH) for the WD, a first set of PRBs configured to be localized and a second set of PRBs configured to be distributed.
According to yet another aspect of the present disclosure, a method in a Wireless Device (WD) for supporting a predetermined set of aggregation levels and for implementing at least one aggregation level and at least one downlink control channel candidate for configuring a downlink control channel for one of a slotted Transmission Time Interval (TTI) and a sub-slotted TTI is provided. The method comprises the following steps: receiving, from a network node, an assigned aggregation level to be monitored by a WD in a communication network; and receiving an assigned downlink control channel candidate from the network node, the network node determining a number of downlink control channel candidates to be monitored by the WD within each of the one of the time slot TTI and the sub-time slot TTI, the number of downlink control channel candidates being based on the assigned aggregation level.
According to this aspect, in some embodiments, receiving from the network node the assigned aggregation level to be monitored by the WD in the communications network comprises receiving from the network node via higher layers and optionally via radio resource control, RRC, signalling the assigned aggregation level to be monitored by the WD in the communications network. In some embodiments, the method further comprises monitoring the assigned aggregation level. In some embodiments, the number of downlink control channel candidates is based at least on a maximum of six downlink control channel candidates to be monitored within each of one of the slotted TTI and the sub-slotted TTI. In some embodiments, the sum of the number of downlink control channel candidates for each aggregation level according to the predetermined set of aggregation levels to be monitored by the WD is at most six downlink control channel candidates. In some embodiments, one of the slot TTI and the sub-slot TTI is a short TTI. In some embodiments, the downlink control channel is a short physical downlink control channel (sPDCCH). In some embodiments, the aggregation level includes a number of short control channel elements (scces). In some embodiments, the number of scces supports a number of downlink control channel candidates defined for each aggregation level of the predetermined set of aggregation levels to be monitored by the WD. In some embodiments, the number of scces is determined based on the system bandwidth. In some embodiments, the number of scces is selected to avoid control overhead of available frequency resources along each of the one of the slot TTI and the sub-slot TTI.
According to yet another aspect of the present disclosure, a Wireless Device (WD) is provided for supporting a predetermined set of aggregation levels and for implementing at least one aggregation level and at least one downlink control channel candidate for configuring a downlink control channel for one of a slotted Transmission Time Interval (TTI) and a sub-slotted TTI. The WD includes processing circuitry configured to: receiving, from a network node, an assigned aggregation level to be monitored by a WD in a communication network; and receiving an assigned downlink control channel candidate from the network node, the network node determining a number of downlink control channel candidates to be monitored by the WD within each of the one of the time slot TTI and the sub-time slot TTI, the number of downlink control channel candidates being based on the assigned aggregation level.
According to this aspect, in some embodiments, the processing circuit is further configured to receive, from the network node via higher layers and optionally via Radio Resource Control (RRC) signaling, the assigned aggregation level to be monitored by the WD in the communication network. In some embodiments, the processing circuit is further configured to monitor the assigned aggregation level. In some embodiments, the number of downlink control channel candidates is based at least on a maximum of six downlink control channel candidates to be monitored within each of one of the slotted TTI and the sub-slotted TTI. In some embodiments, in a high aggregation level, the number of downlink control channel candidates is up to two downlink control channel candidates. In some embodiments, the sum of the number of downlink control channel candidates for each aggregation level according to the predetermined set of aggregation levels to be monitored by the WD is at most six downlink control channel candidates. In some embodiments, one of the slot TTI and the sub-slot TTI is a short TTI. In some embodiments, the downlink control channel is a short physical downlink control channel (sPDCCH). In some embodiments, the aggregation level includes a number of short control channel elements (scces). In some embodiments, the number of scces supports a number of downlink control channel candidates defined for each aggregation level of the predetermined set of aggregation levels to be monitored by the WD. In some embodiments, the number of scces is determined based on the system bandwidth. In some embodiments, the number of scces is selected to avoid control overhead of available frequency resources along each of the slot TTIs and the sub-slot TTIs.
Drawings
A more complete understanding of the present embodiments, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein:
FIG. 1 is a diagram of a time-frequency grid;
fig. 2 is a diagram of a downlink subframe;
fig. 3 is a diagram of a downlink subframe showing a configuration of 10 RB pairs and three ePDCCH regions;
fig. 4 is a diagram of CCE aggregation;
FIG. 5 is a diagram illustrating a search space to be monitored by a wireless device;
FIG. 6 is a flow chart of process steps for PDCCH formation;
fig. 7 illustrates the difference between CCEs and ecces;
fig. 8 is a downlink subframe with 4 parts belonging to ePDCCH;
fig. 9 is a downlink subframe illustrating different mappings of 4 ecces;
fig. 10 is an illustration of sREG configuration based on 12 REs within 1 OFDM;
fig. 11 shows a distributed and centralized configuration of 4 scces;
FIG. 12 shows a distributed and centralized configuration of 4 sCCEs each consisting of 3 sREGs within a 2os-sPDCCH-PRB set;
FIG. 13 shows a distributed and centralized configuration of 4 sCCEs each consisting of 4 sREGs within a 2os-sPDCCH-PRB set;
fig. 14 shows a 3-os-sPDCCH configuration with w scces;
fig. 15 is a block diagram of a network node for configuring a downlink control channel for an sTTI in accordance with the principles of the present disclosure;
fig. 16 is a block diagram of a wireless device for implementing a set of aggregation levels and downlink control channel candidates to configure a downlink control channel for an sTTI in accordance with the principles of the present disclosure;
fig. 17 is an alternative network node for configuring a downlink control channel for an sTTI in accordance with the principles of the present disclosure; and
FIG. 18 is an alternative wireless device for implementing a set of aggregation levels and downlink control channel candidates to configure a downlink control channel for an sTTI in accordance with the principles of the present disclosure;
fig. 19 is a flow diagram of an exemplary process performed in a network node for configuring a downlink control channel for an sTTI, in accordance with the principles of the present disclosure;
fig. 20 is a flow diagram of an exemplary process performed in a wireless device to implement a set of aggregation levels and downlink control channel candidates for configuring downlink control channels for an sTTI, in accordance with the principles of the present disclosure; and
fig. 21A-B show link performance for different CRC lengths for an extended vehicle a (eva) channel and an extended typical city (ETU) channel, respectively.
Detailed Description
Before describing in detail exemplary embodiments, it is noted that the embodiments reside primarily in combinations of device components and processing steps related to defining aggregation levels to be supported for sTTI operations and sPDCCH candidates for each aggregation level, and defining sPDCCH-PRB set sizes for sTTI operations.
Accordingly, the components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.
The present disclosure is described in the context of LTE (i.e., E-UTRAN). It should be understood that the problems and solutions described herein are equally applicable to radio access networks and wireless devices (user equipment (UE)) implementing other access technologies and standards, such as 5G NR. LTE is used as an example technology, and thus the use of LTE in the description is particularly useful for understanding the problem and for solving the problem.
As used herein, relational terms, such as "first" and "second," "top" and "bottom," and the like, may be used solely to distinguish one entity or element from another entity or element without necessarily requiring or implying any physical or logical relationship or order between such entities or elements.
Embodiments described herein may be used to limit the number of blind decodes performed by a wireless device within a 1ms subframe in order to facilitate the implementation and capabilities of the wireless device. The proposed sPDCCH-PRB set configuration is wireless device specific, but it may also be shared between multiple wireless devices. Thus, the network node may be given full flexibility for transmission of sPDCCH. In addition, the sPDCCH-PRB set size definition is based on providing high order diversity and avoiding excessive control overhead within one sTTI.
Throughout this disclosure, it is assumed that the sPDCCH parameters have been pre-configured by higher layer signaling such as RRC of LTE, or predefined in, for example, the LTE specification. A typical sPDCCH parameter is the number of time resources (e.g., OFDM symbols) used for sPDCCH transmission. As an example, for short tti (stti) operation, in the following description, the preconfigured or predefined number of OFDM Symbols (OS) for sPDCCH is 1,2, or 3.
Referring now to fig. 15, components of an example network node 30 for supporting a predetermined set of aggregation levels for configuring downlink control channels for short transmission time intervals (sTTI) are shown. In one embodiment, the network node 30 includes a communication interface 32 and a processing circuit 34. The processing circuitry 34 includes a processor 36 and a memory 38. Memory 38 may include aggregation level and candidate determination code 40, and in some embodiments, aggregation level and candidate determination code 40 may include instructions for implementing one or more of the techniques described herein for network node 30. The memory 38 may comprise any kind of volatile and/or non-volatile memory, such as a cache and/or a buffer memory and/or a RAM (random access memory) and/or a ROM (read only memory) and/or an optical memory and/or an EPROM (erasable programmable read only memory). Such memory may be configured to store code executable by the control circuitry and/or other data, e.g., data relating to communications, e.g., configuration and/or address data for the nodes, etc.
The processor 36 is configured to perform all or some of the processes described herein with respect to the network node 30. In addition to conventional processors and memories and the above described microcontroller arrangement, the processing circuitry 34 may comprise integrated circuits for processing and/or control, e.g. one or more processors and/or processor cores and/or FPGAs (field programmable gate arrays) and/or ASICs (application specific integrated circuits).
The processing circuit 34 may comprise and/or be connected to and/or configured for accessing (e.g. writing to and/or reading from) a memory 38, which may comprise any kind of volatile and/or non-volatile memory, e.g. a cache and/or a buffer memory and/or a RAM (random access memory) and/or a ROM (read only memory) and/or an optical memory and/or an EPROM (erasable programmable read only memory). Such memory 38 may be configured to store code and/or other data executable by the control circuitry, e.g., data related to communications, e.g., configuration and/or calibration of input data, etc. The processing circuitry 34 may be configured to control any of the methods described herein and/or to cause such methods to be performed, for example, by the processor 36, corresponding instructions may be stored in the memory 38, the memory 38 may be readable and/or connected in a readable manner to the processing circuitry 34, in other words, the processing circuitry 34 may comprise a controller, which may comprise a microprocessor and/or microcontroller and/or an FPGA (field programmable gate array) device and/or an ASIC (application specific integrated circuit) device. The processing circuitry 34 may be considered to include, or be connected or connectable to, memory that may be configured to be accessible by the controller and/or the processing circuitry 34 for reading and/or writing.
Referring now to fig. 16, components of an example wireless device 42 that supports a predetermined set of aggregation levels and is operable to implement at least one aggregation level and at least one downlink control channel candidate to configure downlink control channels for short transmission time intervals (sTTI) are provided. Wireless device 42 includes a communication interface 44 and processing circuitry 46, processing circuitry 46 including a processor 48 and memory 50, which may store aggregation level monitoring code 52, and in some embodiments aggregation level monitoring code 52 may include instructions for implementing one or more of the techniques described herein for WD 42. The memory 50 may comprise any kind of volatile and/or non-volatile memory, such as a cache and/or a buffer memory and/or a RAM (random access memory) and/or a ROM (read only memory) and/or an optical memory and/or an EPROM (erasable programmable read only memory). Such memory may be configured to store code executable by the control circuitry and/or other data, e.g., data relating to communications, e.g., configuration and/or address data for the nodes, etc.
Processor 48 is configured to perform all or some of the processes described herein for wireless device 42. In addition to conventional processors and memories and the above-described microcontroller arrangement, the processing circuitry 46 may comprise integrated circuits for processing and/or control, e.g., one or more processors and/or processor cores and/or FPGAs (field programmable gate arrays) and/or ASICs (application specific integrated circuits).
The processing circuit 46 may comprise and/or be connected to and/or configured for accessing (e.g. writing to and/or reading from) the memory 50, the memory 50 may comprise any kind of volatile and/or non-volatile memory, e.g. a cache and/or a buffer memory and/or a RAM (random access memory) and/or a ROM (read only memory) and/or an optical memory and/or an EPROM (erasable programmable read only memory). Such memory 50 may be configured to store code executable by the control circuitry and/or other data, such as data relating to communications, e.g., configuration and/or calibration of input data, etc. The processing circuitry 46 may be configured to control any of the methods described herein and/or cause such methods to be performed, for example, by the processor 48. Corresponding instructions may be stored in the memory 50, the memory 50 may be readable and/or connected in a readable manner to the processing circuitry 46, in other words, the processing circuitry 46 may comprise a controller, which may comprise a microprocessor and/or a microcontroller and/or an FPGA (field programmable gate array) device and/or an ASIC (application specific integrated circuit) device. The processing circuitry 46 may be considered to include or may be connected or connectable to a memory that may be configured to be accessible by the controller and/or the processing circuitry 46 for reading and/or writing.
The term "wireless device" or mobile terminal as used herein may refer to any type of wireless device that communicates with a network node 30 and/or with another wireless device 42 in a cellular or mobile communication system. Examples of wireless devices 42 are User Equipment (UE), target device, device-to-device (D2D) wireless device, machine type wireless device or wireless device capable of machine-to-machine (M2M) communication, PDA, tablet, smart phone, Laptop Embedded Equipment (LEE), Laptop Mounted Equipment (LME), USB dongle, and so forth.
The term "network node" as used herein may refer to any kind of radio base station in a wireless network, which may further include any Base Transceiver Station (BTS), Base Station Controller (BSC), Radio Network Controller (RNC), evolved node B (eNB or eNodeB), NR gbnodeb, NR gbb, node B, multi-standard radio (MSR) radio node (e.g., MSRBS), relay node, donor node controlling relays, radio Access Point (AP), transmission point, transmission node, Remote Radio Unit (RRU), Remote Radio Head (RRH), node in a Distributed Antenna System (DAS), etc.
Although embodiments are described herein with reference to certain functions performed by the network node 30, it should be understood that these functions may be performed in other network nodes and elements. It should also be understood that the functionality of network node 30 may be distributed across a network cloud such that other nodes may perform one or more functions or even portions of the functions described herein.
Referring to fig. 17, an alternative embodiment of a network node 30 for configuring a downlink control channel for a short transmission time interval (sTTI) is shown. In one embodiment, the network node 30 comprises an aggregation level determination module 54 configured to determine a predetermined set of aggregation levels to be monitored by wireless devices 42 in the communication network, each of the aggregation levels comprising a number of short control channel elements (scces); a downlink control channel candidate determination module 56 configured to determine a number of downlink control channel candidates for the wireless device 42 to monitor within each sTTI, the number of downlink channel candidates based at least on a predetermined set of aggregation levels; and a communication interface module 58 configured to assign the set of aggregation levels and downlink control channel candidates to the wireless device 42.
Referring to fig. 18, an alternative embodiment is provided for implementing a wireless device 42 for configuring a set of aggregation levels of downlink control channels and downlink control channel candidates for short transmission time intervals (sTTI). The wireless device 42 comprises a communication interface module 60 configured to receive an assigned set of aggregation levels from the network node 30, each of the aggregation levels comprising a number of short control channel elements (scces), and to receive an assigned downlink control channel candidate from the network node 30, the network node 30 determining a number of downlink control channel candidates that the wireless device 42 is to monitor within each sTTI, the number of downlink channel candidates being based on at least the predetermined set of aggregation levels. The wireless device 42 also includes an aggregation level monitoring module 62 configured to monitor the assigned set of aggregation levels.
Referring to fig. 19, an exemplary method in a network node 30 for supporting a predetermined set of aggregation levels for configuring downlink control channels for short transmission time intervals (sTTI) is provided. In one embodiment, the method comprises: determining at least a subset of a predetermined set of aggregation levels to be monitored by a Wireless Device (WD)42 in a communication network (block S100); and determining a number of downlink control channel candidates to be monitored by WD within each sTTI, the number of downlink control channel candidates being based at least in part on at least a subset of the predetermined set of aggregation levels (block S110).
Referring to fig. 20, a method in a wireless device 42, the wireless device 42 supporting a predetermined set of aggregation levels and for implementing at least one aggregation level and at least one downlink control channel candidate to configure a downlink control channel for a short transmission time interval (sTTI) is provided. The method comprises receiving, from the network node 30, at least an assigned subset of a predetermined set of aggregation levels to be monitored by the WD42 in the communication network (block S120); and receiving the allocated downlink control channel candidates from the network node 30, the network node 30 determining a number of downlink control channel candidates to be monitored by WD42 within each sTTI, the number of downlink control channel candidates being based on at least the assigned subset of the predetermined set of aggregation levels (block S130).
Having generally described some embodiments of the present disclosure, a more detailed description of some embodiments will now be described below.
Aggregation levels to be supported in sTTI operations
It has been recognized that short TTIs may be most beneficial at low to moderate system loads. It has been noted that sTTI operation may have flexible sPDCCH regions. At low to medium load, only a small amount of resources may be needed for the sPDCCH, due to few co-scheduled users and due to high signal to interference plus noise ratio (SINR) (low interference). Thus, the sPDCCH can be designed such that the amount of occupied resources is adapted to the number of co-scheduled users (in DL and UL) and their required aggregation level. Thus, it is expected that the aggregation level configured for the wireless device (e.g., WD 42) will remain low during sTTI operation. As described above, an aggregation level includes a certain number of scces. For example, aggregation level 1 includes one sCCE, aggregation level 2 includes two scces, and aggregation level 4 includes four scces.
Based on this, in one embodiment of the present disclosure, three Aggregation Levels (AL) {1,2, 4}, for sPDCCH supported for short TTI operation may be defined, e.g., up to 4 scces per sPDCCH.
Thus, the wireless device (e.g., WD 42) is able to monitor up to three aggregation levels per sTTI. However, in another embodiment, the wireless device 42 may be configured by higher layers, e.g., by RRC for LTE, or the wireless device 42 may be signaled in the legacy PDCCH (i.e., in the DCI) the number of candidates to monitor per configured aggregation level, with only one, two, or three sPDCCH aggregation levels being monitored per sTTI. E.g. a low aggregation level, e.g. 1 or 2, for efficient resource utilization in good channel conditions and a high aggregation level, e.g. 4, for low channel quality. Thus, the network node 30 may be able to select an appropriate aggregation level set to be configured for each wireless device 42.
sPDCCH candidates to be supported in sTTI operation
For sTTI operation, it has been considered that dynamic switching between short TTIs and 1ms TTIs can be supported. This means that the wireless device 42 may search for 1ms TTI assignments/grants and sTTI assignments/grants in the sub-frame. Since wireless device 42 may monitor additional candidates in the sPDCCH multiple times per subframe, the total number of blind decodes that wireless device 42 needs to perform may increase. Thus, the network facilitates wireless device 42 implementation that it may be beneficial for short TTI operation to keep the additional number of candidates and attempts for Blind Decoding (BD) within a 1ms subframe low. To this end, in one embodiment of the present disclosure, four sPDCCH candidates are defined per wireless device 42 for each sTTI. This embodiment establishes that a low aggregation level, such as AL1 and AL2, may include up to three sPDCCH candidates, while a high aggregation level, such as AL4, may include up to two candidates.
As another embodiment, the candidates per aggregation level to be monitored by the wireless device 42 are defined according to a set of aggregation levels configured for the wireless device 42, as shown in table 3 below. The definition of candidates per aggregation level may be based on the required sPDCCH-PRB set size to be configured. In this disclosure, the sPDCCH-PRB set size is further described below.
Table 3: candidates to be monitored by the wireless device 42 based on its configured aggregation level. This case considers up to four sPDCCH candidates.
In 2 OFDM symbols sTTI, there are six sTTI within a 1ms subframe. If up to four sPDCCH candidates are considered for each sTTI and assuming the same DL/UL sDCI size, the wireless device 42 would need to monitor 24 more candidates within a 1ms subframe for sTTI operation. If the DL/UL sdis of different sizes, 48 additional candidates would need to be monitored within the 1ms subframe. However, if the processing power of the wireless device 42 needs to be further reduced within a 1ms subframe, as an enhancement of the previous embodiment, the number of candidates to monitor may be defined as three. In this embodiment, low polymerization levels, such as AL1 and AL2, may include up to two candidates, while high polymerization levels, such as AL4, include one candidate.
As another embodiment, the candidates per aggregation level to be monitored by the wireless device 42 are based on a set of aggregation levels configured for the wireless device 42, as shown in table 4 below.
Table 4: candidates to be monitored by the wireless device 42 based on its configured aggregation level. This case considers up to three sPDCCH candidates.
Tables 3 and 4 show the feature of limiting the number of sPDCCH candidates to up to 4 candidates. It has then been considered that those candidates are divided between aggregation levels that may be configured for the wireless device 42, which means that each aggregation level may be defined by the number of candidates as described in tables 3 and 4, but in one embodiment the sum of all candidates cannot be greater than 4 or 3. For example, in the last option of table 3, for a total of four candidates for a given aggregation level, the aggregation level configured for the wireless device 42 is {1,2, 4}, where aggregation level 1 has two candidates, aggregation level 2 has one candidate, and aggregation level 4 has one candidate.
Tables 3 and 4 above are merely exemplary. In other embodiments, up to six sPDCCH candidates per WD42 for each sTTI may be considered. For example, a low aggregation level, e.g., 1 and 2, may include up to three candidates, while a high aggregation level, e.g., 4, up to two candidates (in some embodiments only one AL4 candidate may be supported). For example, if WD42 is configured with an aggregation level of {1,2, 4}, the number of sPDCCH candidates may be defined as {2, 2, 1}, to produce a total of 5 candidates per sTTI. In yet another embodiment, for the example where only two aggregation levels are configured for WD42, e.g., {2, 4}, the number of sPDCCH candidates may be defined as {3, 1}, to yield a total of 4 candidates per sTTI. Thus, some embodiments of the present invention provide for limiting the number of sPDCCH candidates to a maximum number of candidates (e.g., 3 candidates as shown in table 4, 4 candidates as shown in table 3, 6 candidates as described above, etc.).
sPDCCH-PRB set configuration for sTTI operation
As described above, wireless device 42 may be configured with one or more sPDCCH-PRB sets that contain the user-specific sTTI search space for wireless device 42 through higher layer signaling. The sPDCCH-PRB set(s) may be configured as localized or distributed. To define how many PRB sets need to be configured for wireless device 42, in one embodiment of the invention, for DMRS based sPDCCH, wireless device 42 is defined two PRB sets, one set configured to be localized and a second set configured to be distributed. A localized sPDCCH-PRB set may be used to allocate sregs that construct the same sCCE in a limited band. This arrangement may utilize scheduling and beamforming gains for DMRS based sPDCCH when CSI is available at the network node 30. The distributed sPDCCH-PRB set may be used to provide robust control signaling and backoff when CSI is limited or unavailable. Further, in this embodiment, for CRS-based sPDCCH, it may be defined that at least one PRB set is configured to be distributed in order to achieve frequency diversity gain. An sPDCCH-PRB set configuration selection may be defined by the network node 30 for each wireless device 42.
Since the sPDCCH-PRB set may consist of groups of PRBs, the network node 30 may have full flexibility to define an appropriate sPDCCH-PRB set size for each wireless device 42 according to the available system bandwidth. Thus, as an embodiment, the sPDCCH-PRB set size may be based on:
support for a suitable number of scces.
-number of OFDM symbols per sPDCCH.
-number of sREGs per sCCE.
Thus, the sPDCCH-PRB set size may be defined as follows:
wherein N isRBIs sPDCCH-PRB set size, NsCCEIs the number of scces to be supported (which is described further below), nr _ of _ sREG _ per _ sCCE is the number of sregs per sCCE, and nr _ of _ OFDM _ symbols _ per sPDCCH is the number of OFDM symbols per sPDCCH. Thus, the definition of the sPDCCH-PRB set can be defined as NsCCEAnd the number of OFDM symbols per sPDCCH and the number of sREG per sCCE.
According to this formula, the masterOne of the factors is NsCCE. Thus, as a further example, NsCCEMay be based on at least:
including the number of scces required to support the number of sPDCCH candidates defined per aggregation level for each wireless device 42.
A limited number of wireless devices 42 with high aggregation level sPDCCH (e.g. AL 4) are supported in the same sTTI, if needed. This is the case for the same sPDCCH-PRB set that may be shared among multiple wireless devices 42.
-system bandwidth.
The number of scces may be chosen in order to avoid excessive control overhead of the available frequency resources along each sTTI.
Thus, in one embodiment, each possible configuration regarding the number of OFDM symbols per sPDCCH, e.g., 1OS, 2OS, and 3OS, supports three different values of N _ sCCE: 4sCCE, 6sCCE, and 8 sCCE. As described above, N _ sCCE-8 sCCE supports up to two candidates (for the case where up to 4 sPDCCH candidates are defined), e.g., AL 4. Furthermore, with 8 scces, the network node 30 may flexibly configure up to two of the following wireless devices 42: which share the same sPDCCH-PRB-set with the sPDCCH with AL4 in the same sTTI. N _ sCCE ═ 6sCCE supports up to three candidates, e.g., AL2 (for both cases where up to 3 or 4 sPDCCH candidates are defined). N _ sCCE ═ 4sCCE supports at least one candidate with AL4, for example.
Based on the above formula, for N _ sCCE ═ 4, 6, and 8sCCE, 1os, 2os, and 3os sPDCCH and the sPDCCH-PRB set size of 1sCCE ═ 3sREG and 1sCCE ═ 4sREG are considered to be defined as one embodiment of the present disclosure, as described below in table 5, table 6, and table 7, respectively.
Table 5: for NsCCEsPDCCH-PRB-set size considering the case of 1os, 2os and 3os sPDCCH and 1sCCE 3sREG and 1sCCE 4sREG 8sCCE
Table 6: for NsCCEsPDCCH-PRB-set size considering the case of 1os, 2os and 3os sPDCCH and 1sCCE 3sREG and 1sCCE 4sREG 6sCCE
Table 7: for NsCCEsPDCCH-PRB-set size considering the case of 1os, 2os and 3os sPDCCH and 1sCCE 3sREG and 1sCCE 4sREG
However, as observed, for example, for the case of 1os-sPDCCH and low system bandwidth (e.g., 5MHz), NsCCE8sCCE may represent a high sPDCCH overhead. Thus, as an additional embodiment, the network node 30 may carefully configure the sPDCCH-PRB set size based on the available system bandwidth.
For normal CP, an LTE subframe lasting 1ms contains 14 OFDM symbols. A new air-gap (NR) subframe has a fixed duration of 1ms and may therefore contain different numbers of OFDM symbols for different subcarrier intervals. For normal CP, an LTE slot corresponds to 7 OFDM symbols. NR slots correspond to 7 or 14 OFDM symbols; at 15kHz subcarrier spacing, a slot with 7 OFDM symbols occupies 0.5 ms. With respect to NR terminology, reference may be made to 3GPP TR 38.802v14.0.0 and subsequent releases.
Alternatively, references herein to short TTIs may be considered sub-or micro-slots in accordance with NR terminology. The micro-slot may have a length of 1 symbol, 2 symbols, 3 or more symbols, or a length between 1 symbol and NR slot lengths minus 1 symbol. A short TTI (or sub-slot) may have a length of 1 symbol, 2 symbols, 3 or more symbols, an LTE slot length (7 symbols), or a length between 1 symbol and the LTE subframe length minus 1 symbol. Short TTIs, subslots, or minislots may be considered to have a length of less than 1ms or less than 0.5 ms.
Thus, as described herein, in one embodiment, there are three aggregation levels for sTTI operation. The wireless device 42 may support these three aggregation levels, but it may be configured by higher layers (e.g., RRC) to monitor only one of them.
In one embodiment, the present disclosure defines a limited number of candidates for sPDCCH in sTTI operation, wherein the definition of the number of candidates per aggregation level depends on the configured set, as shown in tables 3 and 4.
In one embodiment, the present disclosure provides a sPDCCH-PRB set configuration comprising:
for DMRS based sPDCCH, wireless device 42 is defined two sets of PRBs, where one set may be configured as localized and a second set may be configured as distributed;
for CRS based sPDCCH, the disclosure may be defined to configure at least one PRB set as distributed; and
the sPDCCH-PRB set size may be based on three factors, namely the coefficients of N _ scces, the number of OFDM symbols per sPDCCH, and the number of sregs per sCCE.
In one embodiment, a method in a network node 30 is provided for supporting a predetermined set of aggregation levels for configuring a downlink control channel for one of a slotted Transmission Time Interval (TTI) and a sub-slotted TTI. The method comprises determining an aggregation level to be monitored by a wireless device WD42 in the communication network (S100); and determining a number of downlink control channel candidates to be monitored by the WD42 within each of the one of the time slot TTI and the sub-time slot TTI, the number of downlink control channel candidates being based on the aggregation level (S110). A reference to one of a slot TTI and a sub-slot TTI, or to each of one of a slot TTI and a sub-slot TTI, may refer to use in a slot TTI and/or a sub-slot TTI, i.e., one or both of a slot TTI and a sub-slot TTI, i.e., a short TTI. Aspects of the present disclosure apply to one or both of the slotted TTI and the sub-slotted TTI (or micro-slot), i.e., in transmissions using short TTI lengths. In one embodiment, the method further comprises assigning an aggregation level and downlink control channel candidates to the WD 42. In some embodiments, assigning the aggregation level and the downlink control channel candidates to the WD42 comprises assigning the aggregation level and the downlink control channel candidates to the WD42 by higher layers, and optionally by RRC signaling. In some embodiments, determining the number of downlink control channel candidates to be monitored by the WD42 within each of the one of the time-slot TTI and the sub-slot TTI comprises: determining a number of downlink control channel candidates to be monitored by the WD42 within each of the one of the slotted TTI and the sub-slotted TTI based at least on a maximum of six downlink control channel candidates to be monitored within each of the one of the slotted TTI and the sub-slotted TTI. In some embodiments, determining the number of downlink control channel candidates to be monitored by the wireless device within each of the one of the slotted TTI and the sub-slotted TTI comprises: up to two downlink control channel candidates in a high aggregation level are determined. In some embodiments, the sum of the number of downlink control channel candidates for each aggregation level according to the predetermined set of aggregation levels to be monitored by the WD42 is at most six downlink control channel candidates. In some embodiments, one of the slot TTI and the sub-slot TTI is a short TTI. In some embodiments, the downlink control channel is a short physical downlink control channel (sPDCCH). In some embodiments, each aggregation level includes a number of short control channel elements (scces). In some embodiments, the number of scces supports a number of downlink control channel candidates defined for each aggregation level of the predetermined set of aggregation levels to be monitored by the WD 42. In some embodiments, the number of scces is determined based on the system bandwidth. In some embodiments, the number of scces is selected to avoid control overhead of available frequency resources along each of the one of the slot TTI and the sub-slot TTI. In some embodiments, the method further comprises determining a downlink control channel physical resource block set size for each WD 42. In some embodiments, determining the PRB set size for each WD42 is based at least on the number of scces, the number of orthogonal frequency division multiplexing, OFDM, symbols per control channel, and the number of short resource element groups (sregs) per sCCE. In some embodiments, the WD42 is defined two sets of PRBs for a demodulation reference signal (DMRS) -based short physical downlink control channel (sPDCCH), a first set of PRBs configured to be localized and a second set of PRBs configured to be distributed.
In another embodiment, a network node 30 is provided for supporting a predetermined set of aggregation levels for configuring a downlink control channel for one of a slotted Transmission Time Interval (TTI) and a sub-slotted TTI. The network node 30 comprises a processing circuit 34 configured to: determining an aggregation level to be monitored by a wireless device WD42 in a communication network; and determining a number of downlink control channel candidates to be monitored by the WD42 within each of the one of the time slot TTI and the sub-time slot TTI, the number of downlink control channel candidates being based on the aggregation level. In some embodiments, the processing circuit 34 is further configured to assign an aggregation level and downlink control channel candidates to the WD 42. In some embodiments, processing circuitry 34 is further configured to assign aggregation levels and downlink control channel candidates to WD42 through higher layers and optionally through RRC signaling. In some embodiments, the processing circuitry 34 is further configured to determine a number of downlink control channel candidates to be monitored by the WD42 within each of one of the slotted TTI and the sub-slotted TTI based at least on a maximum of six downlink control channel candidates to be monitored within each of one of the slotted TTI and the sub-slotted TTI. In some embodiments, the processing circuitry 34 is further configured to determine up to two downlink control channel candidates in a high aggregation level. In some embodiments, the sum of the number of downlink control channel candidates for each aggregation level according to the predetermined set of aggregation levels is at most six downlink control channel candidates. In some embodiments, one of the slot TTI and the sub-slot TTI is a short TTI. In some embodiments, the downlink control channel is a short physical downlink control channel (sPDCCH). In some embodiments, the aggregation level includes a number of short control channel elements (scces). In some embodiments, the number of scces supports a number of downlink control channel candidates defined for each aggregation level of the predetermined set of aggregation levels to be monitored by the WD 42. In some embodiments, the number of scces is determined based on the system bandwidth. In some embodiments, the number of scces is selected to avoid control overhead of available frequency resources along each of the one of the slot TTI and the sub-slot TTI. In some embodiments, the processing circuitry 34 is further configured to determine a downlink control channel physical resource block, PRB, set size for each WD 42. In some embodiments, the processing circuitry 34 is further configured to determine the PRB set size for each WD42 based at least on the number of scces, the number of orthogonal frequency division multiplexing, OFDM, symbols per control channel, and the number of short resource element groups (sregs) per sCCE. In some embodiments, the processing circuitry 34 is further configured to define two sets of PRBs for a demodulation reference signal (DMRS) -based short physical downlink control channel (sPDCCH) to the WD42, the first set of PRBs being configured to be localized and the second set of PRBs being configured to be distributed.
In another embodiment, a method in a wireless device WD42 is provided for supporting a predetermined set of aggregation levels and for implementing at least one aggregation level and at least one downlink control channel candidate to configure a downlink control channel for one of a slotted Transmission Time Interval (TTI) and a sub-slotted TTI. The method comprises receiving, from the network node 30, an assigned aggregation level to be monitored by the WD42 in the communication network (S120); and receiving the assigned downlink control channel candidate from the network node 30, the network node 30 determining a number of downlink control channel candidates to be monitored by the WD42 within each of the one of the slotted TTI and the sub-slotted TTI, the number of downlink control channel candidates being based on the assigned aggregation level (S130). In some embodiments, the method of receiving, from the network node 30, an assigned aggregation level to be monitored by the WD42 in the communication network comprises: radio Resource Control (RRC) signaling of the assigned AT aggregation level to be monitored by the WD42 in the communication network is received via higher layers and optionally from the network node 30. In some embodiments, the method further comprises monitoring the assigned aggregation level. In some embodiments, the number of downlink control channel candidates is based at least on a maximum of six downlink control channel candidates to be monitored within each of one of the slotted TTI and the sub-slotted TTI. In some embodiments, in a high aggregation level, the number of downlink control channel candidates is up to two downlink control channel candidates. In some embodiments, the sum of the number of downlink control channel candidates for each aggregation level according to the predetermined set of aggregation levels to be monitored by the WD42 is at most six downlink control channel candidates. In some embodiments, one of the slot TTI and the sub-slot TTI is a short TTI. In some embodiments, the downlink control channel is a short physical downlink control channel (sPDCCH). In some embodiments, the aggregation level includes a number of short control channel elements (scces). In some embodiments, the number of scces supports a number of downlink control channel candidates defined for each aggregation level of the predetermined set of aggregation levels to be monitored by the WD 42. In some embodiments, the number of scces is determined based on the system bandwidth. In some embodiments, the number of scces is selected to avoid control overhead of available frequency resources along each of the slot TTIs and the sub-slot TTIs.
In yet another embodiment, a Wireless Device (WD)42 is provided for supporting a predetermined set of aggregation levels and for implementing at least one aggregation level and at least one downlink control channel candidate to configure a downlink control channel for one of a slotted Transmission Time Interval (TTI) and a sub-slotted TTI. WD42 includes processing circuitry 46 configured to: receiving, from the network node 30, an assigned aggregation level to be monitored by the WD42 in the communication network; receiving the assigned downlink control channel candidates from the network node 30, the network node 30 determines a number of downlink control channel candidates to be monitored by the WD42 within each of the one of the slotted TTI and the sub-slotted TTI, the number of downlink control channel candidates being based on the assigned aggregation level. In some embodiments, the processing circuit 46 is further configured to receive, from the network node 30 via higher layers and optionally via Radio Resource Control (RRC) signaling, the assigned aggregation level to be monitored by the WD42 in the communication network. In some embodiments, the processing circuit 46 is further configured to monitor the assigned aggregation level. In some embodiments, the number of downlink control channel candidates is based at least on a maximum of six downlink control channel candidates to be monitored within each of one of the slotted TTI and the sub-slotted TTI. In some embodiments, in a high aggregation level, the number of downlink control channel candidates is up to two downlink control channel candidates. In some embodiments, the sum of the number of downlink control channel candidates for each aggregation level according to the predetermined set of aggregation levels is at most six downlink control channel candidates. In some embodiments, one of the slot TTI and the sub-slot TTI is a short TTI. In some embodiments, the downlink control channel is a short physical downlink control channel (sPDCCH). In some embodiments, the aggregation level includes a number of short control channel elements (scces). In some embodiments, the number of scces supports a number of downlink control channel candidates defined for each aggregation level of the predetermined set of aggregation levels to be monitored by the WD 42. In some embodiments, the number of scces is selected to avoid control overhead of available frequency resources along each sTTI.
Some further embodiments may include multiplexing sPDCCH for different WD42 within the same search space region for sTTI.
Still additional embodiments of the present disclosure may include limiting blind decoding on PDCCH. Since PDCCH may be used to transmit DCI and support dynamic switching between short TTI and 1ms TTI, WD42 may have to search each subframe for both 1ms DCI and DCI in PDCCH. Therefore, the total number of blind decodings in the PDCCH may increase. One exemplary method of limiting the number of blind decodes may be a generic format for sTTI and 1ms TTI. Another exemplary approach may be to define the search space for the sDCI transmitted on the PDCCH as a subset of the search space for the 1ms TTI DCI.
Still other embodiments may include limiting blind decoding on the sPDCCH according to additional techniques. For example, an uplink grant and a downlink assignment in DCI may have slightly different fields, e.g., there may be dedicated bits in the DL and no such dedicated bits in the UL. Although the uplink grant and downlink allocation may have different amounts of bits in the DCI, these formats may be blindly decoded on the same sCCE. Thus, to limit blind decoding, the design of the DCI format may be configured to be the same size for all grants, and the bit field may indicate whether the DCI is an uplink grant or a downlink allocation. This approach can be considered similar to the flag for Format 0/Format 1A differentiation. In further embodiments, padding bits may be used in addition to the indication bits, in case the number of required bits is different for uplink grants and downlink assignments. In one embodiment, a single size may be defined for DL and UL dci in order to limit the number of blind decodings of WD 42.
Still other embodiments of the present disclosure may include increasing the sPDCCH Cyclic Redundancy Check (CRC) length. For example, increasing the sPDCCH CRC length from 16 bits to 24 bits has been considered, e.g., to reduce the false detection rate and avoid an additional pruning (pruning) algorithm in the WD 42. In some embodiments, a longer CRC may have some impact on control channel performance. Fig. 21A-B show the sPDCCH block error rate (BLER) of AL1 in a 10MHz system bandwidth, where the sPDCCH-PRB set size is 18 PRBs, assuming a distributed and centralized configuration of scces 0. Exemplary results for an extended vehicle a (eva) channel are shown in fig. 21A and for an extended typical city (ETU) channel, both at 3km/h, are shown in fig. 21B. Figures 21A-B show simulations for both the standard 16-bit CRC and the performance when using an 8 additional bit, i.e. a 24-bit CRC. As shown in fig. 21A-B, a 24-bit CRC increases the code rate and BLER, resulting in a loss of about 1.5-2 dB. Thus, fig. 21A-B illustrate the link performance for different sREG mappings for one sCCE sPDCCH, both figures including curve sets with different payloads of 14 and 34 bits (excluding CRC) and CRC lengths of 16 or 24 bits. In some embodiments, the loss in demodulation performance may be compensated for by using a higher AL, which may also result in more scheduling constraints and greater control overhead. In some embodiments, it may be advantageous to compare the benefit of increasing the sPDCCH CRC length to the signal-to-noise ratio (SNR) loss resulting from the increased coding rate.
Some embodiments of the disclosure are as follows:
determining a predetermined set of aggregation levels to be monitored by a wireless device in a communication network, each of the aggregation levels comprising a number of short control channel elements, scces;
determining a number of downlink control channel candidates to be monitored by the wireless device within each sTTI, the number of downlink channel candidates based at least on a predetermined set of aggregation levels; and
assigning a set of aggregation levels and the downlink control channel candidates to the wireless device.
a processing circuit comprising a memory and a processor, the memory in communication with the processor, the memory having instructions that, when executed by the processor, configure the processor to:
determining a predetermined set of aggregation levels to be monitored by a wireless device in a communication network, each of the aggregation levels comprising a number of short control channel elements, scces;
determining a number of downlink control channel candidates to be monitored by the wireless device within each sTTI, the number of downlink channel candidates based at least on a predetermined set of aggregation levels; and
a communication interface configured to:
assigning a set of aggregation levels and the downlink control channel candidates to the wireless device.
Embodiment 18 the network node of embodiment 12, wherein the number of scces supports wireless devices with an aggregation level greater than a predetermined level.
Embodiment 19 the network node of embodiment 12, wherein the number of scces is determined based on the system bandwidth.
Embodiment 20. the network node according to embodiment 12, wherein the number of scces is selected to avoid control overhead along the available frequency resources per sTTI.
Embodiment 21 the network node of embodiment 12, wherein the number of aggregation levels to be monitored by each wireless device is three.
Embodiment 22 the network node of embodiment 12, wherein the processor is further configured to assign the wireless device a set of aggregation levels and downlink control channel candidates through at least one of radio resource control, RRC, signaling and physical downlink control channel, PDCCH, signaling.
Embodiment 23. a method in a wireless device for implementing a set of aggregation levels and downlink control channel candidates to configure a downlink control channel for a short transmission time interval, sTTI, the method comprising:
receiving, from a network node, an assigned set of aggregation levels, each of the aggregation levels comprising a number of short control channel elements, scces;
monitoring a set of assignments of aggregation levels; and
receiving an assigned downlink control channel candidate from the network node, the network node determining a number of downlink control channel candidates for the wireless device to monitor within each sTTI, the number of downlink channel candidates based at least on a set of assignments of aggregation levels.
Embodiment 24. the method according to embodiment 23, wherein the downlink control channel is a short physical downlink control channel, sPDCCH.
Embodiment 25. the method of embodiment 23, wherein the number of scces supports a number of downlink control channel candidates defined for each aggregation level set of the wireless device.
Embodiment 26 the method of embodiment 23, wherein the number of scces supports wireless devices with aggregation levels greater than a predetermined level.
Embodiment 27. the method of embodiment 23, wherein the number of scces is determined based on the system bandwidth.
Embodiment 28. the method of embodiment 23, wherein the number of scces is selected to avoid control overhead along the available frequency resources per sTTI.
Embodiment 29 the method of embodiment 23, wherein the number of aggregation levels to be monitored by the wireless device is three.
Embodiment 30. a wireless device for enabling configuration of a set of aggregation levels of downlink control channels and downlink control channel candidates for a short transmission time interval, sTTI, the wireless device comprising:
a communication interface configured to:
receiving an assigned set of aggregation levels from a network node, each of the aggregation levels comprising a number of short control channel elements, scces; and
receiving an assigned downlink control channel candidate from the network node, the network node determining a number of downlink control channel candidates for the wireless device to monitor within each sTTI, the number of downlink channel candidates based at least on a set of assignments of aggregation levels; and
a processing circuit comprising a memory and a processor, the memory in communication with the processor, the memory having instructions that, when executed by the processor, configure the processor to:
monitoring the assigned aggregation level set;
embodiment 31. the wireless device of embodiment 30, wherein the downlink control channel is a short physical downlink control channel, sPDCCH.
Embodiment 32. the wireless device of embodiment 30, wherein the number of scces supports a number of downlink control channel candidates defined for each aggregation level set of the wireless device.
Embodiment 33. the wireless device of embodiment 30, wherein the number of scces supports wireless devices with aggregation levels greater than a predetermined level.
Embodiment 34 the wireless device of embodiment 30, wherein the number of scces is determined based on the system bandwidth.
Embodiment 35. the wireless device of embodiment 30, wherein the number of scces is selected to avoid control overhead of available frequency resources along each sTTI.
Embodiment 37. a network node for configuring a downlink control channel for a short transmission time interval, sTTI, the network node comprising:
an aggregation level determination module configured to:
determining a predetermined set of aggregation levels to be monitored by a wireless device in a communication network, each of the aggregation levels comprising a number of short control channel elements, scces;
a downlink control channel candidate determination module configured to:
determining a number of downlink control channel candidates to be monitored by the wireless device within each sTTI, the number of downlink channel candidates being based at least on a predetermined set of aggregation levels; and
a communication interface module configured to:
assigning the set of aggregation levels and the downlink control channel candidates to the wireless device.
Embodiment 38. a wireless device for implementing a set of aggregation levels and downlink control channel candidates to configure a downlink control channel for a short transmission time interval, sTTI, the wireless device comprising:
a communication interface module configured to:
receiving, from a network node, an assigned set of aggregation levels, each of the aggregation levels comprising a number of short control channel elements, scces; and
receiving an assigned downlink control channel candidate from the network node, the network node determining a number of downlink control channel candidates to be monitored by the wireless device within each sTTI, the number of downlink channel candidates based at least on a predetermined set of aggregation levels; and
an aggregation level monitoring module configured to:
the assigned aggregation level set is monitored.
As will be appreciated by one skilled in the art, the concepts described herein may be embodied as methods, data processing systems, and/or computer program products. Accordingly, the concepts described herein may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects all generally referred to herein as a "circuit" or "module. Furthermore, the present disclosure may take the form of a computer program product on a tangible computer-usable storage medium having computer program code embodied in the medium that is executable by a computer. Any suitable tangible computer readable medium may be utilized including hard disks, CD-ROMs, electronic memory devices, optical memory devices, or magnetic memory devices.
Some embodiments are described herein with reference to flowchart illustrations and/or block diagrams of methods, systems, and computer program products. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer (to thereby create a special purpose computer), special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory or storage medium that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function/act specified in the flowchart and/or block diagram block or blocks.
The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.
It should be understood that the functions/acts noted in the blocks may occur out of the order noted in the operational illustrations. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality/acts involved. Although some of the figures include arrows on communication paths to illustrate the primary direction of communication, it is to be understood that communication may occur in the opposite direction to the depicted arrows.
Computer program code for performing the operations of the concepts described herein may be in an object oriented programming language (e.g., XML)
Or C + +. However, the computer program code for carrying out operations of the present disclosure may also be written in conventional procedural programming languages, such as the "C" programming language. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer. In the latter scenario, the remote computer may be connected to the user's computer through a Local Area Network (LAN) or a Wide Area Network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet service provider).
Many different embodiments have been disclosed herein in connection with the above description and the accompanying drawings. It will be understood that each combination and sub-combination of the embodiments described and illustrated in the text is intended to be unduly repetitious and confusing. Thus, all embodiments may be combined in any way and/or combination, and the present specification, including the drawings, should be construed to constitute a complete written description of all combinations and subcombinations of the embodiments described herein, and of the manner and process of making and using them, and shall support claims to any such combination or subcombination.
It will be appreciated by persons skilled in the art that the embodiments described herein are not limited to what has been particularly shown and described hereinabove. In addition, unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. Many modifications and variations are possible in light of the above teaching, which is limited only by the following claims.
Claims (56)
1. A method in a network node (30) for supporting a predetermined set of aggregation levels for configuring a downlink control channel for one of a slotted transmission time interval, TTI, and a sub-slotted TTI, the method comprising:
determining (S100) an aggregation level of the predetermined set of aggregation levels to be monitored by a wireless device WD (42) in the communication network; and
determining (S110) a number of downlink control channel candidates for the WD (42) to monitor within each of the one of the time-slot TTI and the sub-slot TTI, the number of downlink control channel candidates being based on the aggregation level.
2. The method of claim 1, further comprising:
assigning the aggregation level and the downlink control channel candidate to the WD (42).
3. The method of claim 2, wherein assigning the aggregation level and the downlink control channel candidate to the WD (42) comprises assigning the aggregation level and the downlink control channel candidate to the WD (42) by a higher layer and optionally by RRC signaling.
4. The method of any one of claims 1-3, wherein determining the number of downlink control channel candidates that the WD (42) is to monitor within each of the one of the time-slot TTI and the sub-slot TTI comprises: determining at least the number of downlink control channel candidates that the WD (42) is to monitor within each of the one of the slotted TTI and the sub-slotted TTI based at least on a maximum of six downlink control channel candidates to monitor within each of the one of the slotted TTI and the sub-slotted TTI.
5. The method of any of claims 1-4, wherein determining the number of downlink control channel candidates that the wireless device is to monitor within each of the one of the slotted TTI and the sub-slotted TTI comprises: up to two downlink control channel candidates in a high aggregation level are determined.
6. The method according to any of claims 1-5, wherein the sum of the number of downlink control channel candidates for each aggregation level of the predetermined set of aggregation levels to be monitored by the WD (42) is at most six downlink control channel candidates.
7. The method of any of claims 1-6, wherein the one of the slotted TTI and the sub-slotted TTI is a short TTI.
8. The method according to any of claims 1-7, wherein the downlink control channel is a short physical downlink control channel, sPDCCH.
9. The method according to any of claims 1-8, wherein the aggregation level comprises a number of short control channel elements, scces.
10. The method according to claim 9, wherein the number of scces supports a number of downlink control channel candidates defined per aggregation level of the predetermined set of aggregation levels to be monitored by the WD (42).
11. The method according to any of claims 9-10, wherein the number of scces is determined based on system bandwidth.
12. The method according to any of claims 9-11, wherein the number of scces is selected to avoid control overhead of available frequency resources along each of the one of the slot TTI and the sub-slot TTI.
13. The method according to any of claims 1-12, further comprising determining a downlink control channel physical resource block, PRB, set size for each WD (42).
14. The method according to claim 13, wherein determining the PRB set size for each WD (42) is based at least on the number of scces, a number of orthogonal frequency division multiplexing, OFDM, symbols per control channel, and a number of short resource element groups, sregs, per sCCE.
15. The method according to any of claims 13-14, wherein for a demodulation reference signal, DMRS, based short physical downlink control channel, sPDCCH, the WD (42) is defined with two sets of PRBs, a first set of PRBs being configured to be localized and a second set of PRBs being configured to be distributed.
16. A network node (30) for supporting a predetermined set of aggregation levels for configuring a downlink control channel for one of a slotted transmission time interval, TTI, and a sub-slotted TTI, the network node (30) comprising processing circuitry (34), the processing circuitry (34) configured to:
determining an aggregation level to be monitored by a wireless device WD (42) in a communication network; and
determining a number of downlink control channel candidates for the WD (42) to monitor within each of the one of the time-slot TTI and the sub-slot TTI, the number of downlink control channel candidates being based on the aggregation level.
17. The network node (30) of claim 16, wherein the processing circuit (34) is further configured to assign the aggregation level and the downlink control channel candidate to the WD (42).
18. The network node (30) of claim 17, wherein the processing circuit (34) is further configured to assign the aggregation level and the downlink control channel candidate to the WD (42) through higher layers and optionally through RRC signaling.
19. The network node (30) of any one of claims 16-18, wherein the processing circuit (34) is further configured to: determining the number of downlink control channel candidates to be monitored by the WD (42) within each of the one of the time-slot TTI and the sub-slot TTI based at least on a maximum of six downlink control channel candidates to be monitored within each of the one of the time-slot TTI and the sub-slot TTI.
20. The network node (30) of any of claims 16-19, wherein the processing circuit (34) is further configured to determine up to two downlink control channel candidates in a high aggregation level.
21. The network node (30) according to any of claims 16-20, wherein the sum of the number of downlink control channel candidates for each aggregation level according to the predetermined set of aggregation levels to be monitored by the WD (42) is at most six downlink control channel candidates.
22. The network node (30) of any of claims 16-21, wherein the one of the timeslot TTI and the sub-timeslot TTI is a short TTI.
23. The network node (30) according to any one of claims 16-22, wherein the downlink control channel is a short physical downlink control channel, sPDCCH.
24. The network node (30) according to any one of claims 16-23, wherein the aggregation level comprises a number of short control channel elements, scces.
25. The network node (30) of claim 24, wherein the number of scces supports a number of downlink control channel candidates defined per aggregation level of the predetermined set of aggregation levels to be monitored by the WD (42).
26. The network node (30) according to any one of claims 24-25, wherein the number of scces is determined based on a system bandwidth.
27. The network node (30) of any of claims 24-26, wherein the number of scces is selected to avoid control overhead of available frequency resources along each of the one of the slot TTI and the sub-slot TTI.
28. The network node (30) according to any of claims 16-27, wherein the processing circuitry (34) is further configured to determine a downlink control channel physical resource block, PRB, set size for each WD (42).
29. The network node (30) of claim 28, wherein the processing circuitry (34) is further configured to determine a PRB set size for each WD (42) based at least on the number of scces, the number of orthogonal frequency division multiplexing, OFDM, symbols per control channel, and the number of short resource element groups, sregs, per sCCE.
30. The network node (30) of any one of claims 28-29, wherein the processing circuit (34) is further configured to: for a short physical downlink control channel, sPDCCH, based on a demodulation reference signal, DMRS, the WD (42) is defined with two sets of PRBs, a first set of PRBs being configured to be localized and a second set of PRBs being configured to be distributed.
31. A method in a wireless device, WD, (42) for supporting a predetermined set of aggregation levels and for implementing at least one aggregation level and at least one downlink control channel candidate for configuring a downlink control channel for one of a slotted transmission time interval, TTI, and a sub-slotted TTI, the method comprising:
receiving (S120), from a network node (30), an assigned aggregation level to be monitored by the WD (42) in a communication network; and
receiving (S130), from the network node (30), the assigned downlink control channel candidate, the network node (30) determining a number of downlink control channel candidates for the WD (42) to monitor within each of the one of the time-slot TTI and the sub-time-slot TTI, the number of downlink control channel candidates being based on the assigned aggregation level.
32. The method of claim 31, wherein receiving the assigned aggregation level from the network node (30) to be monitored by the WD (42) in the communication network comprises receiving the assigned aggregation level from the network node (30) to be monitored by the WD (42) in the communication network via higher layers and optionally over radio resource control, RRC.
33. The method of any of claims 31-32, further comprising monitoring the assigned aggregation level.
34. The method of any of claims 31-33, wherein the number of downlink control channel candidates is based at least on a maximum of six downlink control channel candidates to be monitored within each of the one of the time-slot TTI and the sub-slot TTI.
35. The method according to any of claims 31-34, wherein in a high aggregation level, the number of downlink control channel candidates is up to two downlink control channel candidates.
36. The method according to any of claims 31-35, wherein the sum of the number of downlink control channel candidates for each aggregation level to be monitored by the WD (42) according to the predetermined set of aggregation levels is at most six downlink control channel candidates.
37. The method of any of claims 31-36, wherein the one of the slotted TTI and the sub-slotted TTI is a short TTI.
38. The method according to any of claims 31-37, wherein the downlink control channel is a short physical downlink control channel, sPDCCH.
39. The method according to any of claims 31-38, wherein the aggregation level comprises a number of short control channel elements, scces.
40. The method according to claim 39, wherein the number of sCCEs supports a number of downlink control channel candidates defined per aggregation level of the predetermined set of aggregation levels to be monitored by the WD (42).
41. The method of any of claims 39-40, wherein the number of sCCEs is determined based on system bandwidth.
42. The method according to any of claims 39-41, wherein the number of sCCEs is selected to avoid control overhead of available frequency resources along each of the one of the slot TTI and the sub-slot TTI.
43. A wireless device, WD, (42), the WD (42) being configured to support a predetermined set of aggregation levels and to implement at least one aggregation level and at least one downlink control channel candidate to configure a downlink control channel for one of a timeslot transmission time interval, TTI, and a sub-timeslot TTI, the WD (42) comprising processing circuitry (46), the processing circuitry (46) being configured to:
receiving, from a network node (30), an assigned aggregation level to be monitored by the WD (42) in a communication network; and
receive an assigned downlink control channel candidate from the network node (30), the network node (30) determining a number of downlink control channel candidates for the WD (42) to monitor within each of the one of the time-slot TTI and the sub-time-slot TTI, the number of downlink control channel candidates being based on the assigned aggregation level.
44. The WD (42) of claim 43, wherein the processing circuit (46) is further configured to receive the assigned aggregation level to be monitored by the WD (42) in the communication network from the network node (30) via higher layers and optionally through Radio Resource Control (RRC) signaling.
45. The WD (42) of any of claims 43-44, wherein the processing circuit (46) is further configured to monitor the assigned aggregation level.
46. The WD (42) of any of claims 43-45, wherein the number of downlink control channel candidates is based at least on a maximum of six downlink control channel candidates to be monitored within each of the one of the time-slot TTI and the sub-slot TTI.
47. The WD (42) of any of claims 43-46, wherein the number of downlink control channel candidates is up to two downlink control channel candidates in a high aggregation level.
48. The WD (42) of any of claims 43-47, wherein the sum of the number of downlink control channel candidates for each aggregation level according to the predetermined set of aggregation levels to be monitored by the WD (42) is at most six downlink control channel candidates.
49. The WD (42) of any of claims 43-48, wherein the one of the time-slot TTI and the sub-slot TTI is a short TTI.
50. The WD (42) according to any one of claims 43-49, wherein the downlink control channel is a short physical downlink control channel, sPDCCH.
51. The WD (42) according to any of claims 43-50, wherein the aggregation level comprises a number of short control channel elements, sCCEs.
52. The WD (42) of claim 51, wherein the number of sCCEs supports a number of downlink control channel candidates defined per aggregation level of the predetermined set of aggregation levels to be monitored by the WD (42).
53. The WD (42) according to any one of claims 51-52, wherein the number of sCCEs is determined based on a system bandwidth.
54. The WD (42) of any of claims 51-53, wherein the number of sCCEs is selected to avoid control overhead along each available frequency resource of the one of the slot TTI and the sub-slot TTI.
55. A network node (30), the network node (30) supporting a predetermined set of aggregation levels for configuring a downlink control channel for one of a slotted transmission time interval, TTI, and a sub-slotted TTI, the network node comprising an aggregation level determination module (54), the aggregation level determination module (54) being configured to:
determining an aggregation level to be monitored by a wireless device WD (42) in a communication network; and
determining a number of downlink control channel candidates by the WD (42) to monitor within each of the one of the time-slot TTI and the sub-slot TTI, the number of downlink control channel candidates being based on the aggregation level.
56. A wireless device, WD, (42), the WD (42) being configured to support a predetermined set of aggregation levels and to implement at least one aggregation level and at least one downlink control channel candidate to configure a downlink control channel for one of a slotted transmission time interval, TTI, and a sub-slotted TTI, the WD (42) comprising a communication interface module (60), the communication interface module (60) being configured to:
receiving, from a network node (30), an assigned aggregation level to be monitored by the WD (42) in a communication network; and
receive an assigned downlink control channel candidate from the network node (30), the network node (40) determining a number of downlink control channel candidates to be monitored by the WD (42) within each of the one of the time-slot TTI and the sub-slot TTI, the number of downlink control channel candidates being based on the assigned aggregation level.
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